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How to Control Black Spot on Roses

By Stan DeFreitas ; Updated September 21, 2017

Black spot fungus is a problem of a fungus that grows into the leaves of roses, causing them to drop early. Find out how black spot fungus can cause a rose to die with help from an urban horticulturist and gardening adviser in this free video on growing roses.

Transcript

Hi I'm Stan DeFreitas, Mr. Green Thumb. One of the major problems with roses is black spot fungus. Now the black spot fungus as the name would imply is a little fungal problem that actually grows into the leaf. You know many of the fungal problems we have are parasitic and by that I mean they grow into the leaf, they actually kind of eat the leaf and that causes the leaves to drop early. The problem with roses if you don't control black spot is it will be totally denuded and after about the second time the rose gets totally denuded it normally dies. Now we have got some black spot over here and you can see with this black spot, just as the name implies it has little tiny black spots that get larger as the spores start to grow into the foliage. Now you can go in and pick off some of those leaves, that is a good idea. I take a little paper sack out daily and look for these little tiny spots and catch them early. If you catch them at this stage it is much easier to keep black spot under control. Remember every time a raindrop or watering hits that black spot, spores bounce off on to th leaves below and Johnny Appleseed like you tend to have more black spot over the base of the plant. You can spray with a good fungicide. I would do a good fungicide probably weekly and I would use either Funginex or Dithane M-45, spray the plant from head to toe, underneath and on top of the foliage and you should keep that foliage looking good. Good foliage means good flowers. For askmrgreenthumb.com, I'm Stan DeFreitas.

About the Author

Stan DeFreitas, also known as "Mr. Green Thumb," has experience as an urban horticulturist working for the Pinellas County Extension Service and has taught horticulture at the St. Petersburg College. "Mr. Green Thumb" has spread gardening know-how on radio, TV and newspaper columns in both the Clearwater Sun and the Tampa Tribune. DeFreitas is the number one gardening adviser in the state of Florida, was the first to establish a "community garden" in Pinellas County and helped start the first Master Garden Program in Pinellas County. DeFreitas was also twice Jaycees Horticulture "Man of the Year" was awarded the landscape design award from the city of St. Petersburg Beach, and he was the host of the highest-rated garden show on local PBS.